1. Field of the Invention
The present invention relates to a blood component analysis system. More particularly, the present invention relates to a method of removing abnormal data generated due to internal and external factors, and to a blood component spectroscopy analysis system employing the same.
2. Description of the Related Art
The measurement of a vital signal using a non-invasive method is an important issue in the field of current medical engineering, and methods of measuring various physiological variables have been developed. In particular, various approaches for analyzing blood components without collecting blood have been published, and studies on analysis of blood components without collecting blood have been undertaken. For example, in a method of analyzing blood components using spectroscopy, without collecting blood, a patient does not suffer pain and is not exposed to potential infection, and the result of analysis can be obtained in real time. Due to these advantages and the development of related technology, generalized techniques for conventional equipment for measuring an oxygen saturation have been applied to medical instruments for analyzing blood components such as hemoglobin and glucose. Such medical instruments use a method of analyzing a blood component by measuring a difference in an amount of light of different wavelengths absorbed by a human body using light having a specific wavelength reacting with the blood component.
A photo-plethysmographic (PPG) signal generated when spectroscopy is used includes a pulsatile component and a non-pulsatile component. The PPG signal will be described in detail with reference to FIG. 1. In FIG. 1, “Io” denotes an amount of light radiated to a human body, “It” denotes an amount of light passing through the human body, “Ia” denotes an amount of light absorbed by the human body, “To” denotes a heart beat period, “Ip” denotes a maximum point of a pulsatile component, “Iv” denotes a minimum point of the pulsatile component, “P1” denotes a variation of light intensity due to the pulsatile component, i.e., an alternating current (AC) component, and “P2” denotes a variation of light intensity due to a non-pulsatile component, i.e., a direct current (DC) component. Components absorbing the light radiated to the human body are largely divided into non-pulsatile components, i.e., “P2” components such as bones and vital tissue which do not change with time, and arterial pulsatile components, i.e., “P1” components which change with time due to heart beats.
Accurately measuring the amount of light absorbed by the pulsatile components changing with time is essential to a method of analyzing a blood component using a ratiometric. However, the amplitude and the base line of the PPG signal frequently change according to internal factors, such as breathing, blood pressure, pulse rate, body temperature, a state of blood vessels, or an autonomic nervous system, and to external factors such as spontaneous or non-spontaneous motion. In quantitative terms, as compared to the amount of light absorbed by a non-pulsatile component, typically the amplitude of a pulsatile component changes within a range of 2 through 5%, and the base line of the PPG signal changes within a range of 3 through 5%. These changes in the amplitude of the pulsatile component and the base line of the PPG signal due to an internal factor causes abnormal data. As a result, errors occur in the analysis of a blood component using spectroscopy.
Current techniques remove abnormal data generated only due to external factors, such as motion-induced noise and an unstable contact of a probe, in a system for measuring oxygen saturation. Further, many current techniques require separate hardware to measure the external factors. Finally, in these current techniques, a physiological signal such as an oxygen saturation signal is measured after a predetermined time has passed until a patient becomes physiologically stable, and therefore, a lengthy measuring time is required.